This invention relates to an image sensor for introducing an image to a computer or the like. More particularly, the invention relates to a card-type image sensor having an interface for interfacing a computer or the like.
Computers are becoming increasingly small in size and even computers as small as one's hand have made their appearance. Since the limitation upon the size of the recording medium in these small-size computers is greater than in the case of desktop computers, small-size computers are provided with a card slot into which a PCMCIA card can be directly inserted instead of a floppy disk drive.
Usually a memory card or fax card is capable of being inserted into the card slot so that a variety of applications can be accommodated.
In terms of structure, these cards generally have a board and an interface connector as well as a frame-shaped member for holding the board and the connector. The frame is embraced from above and below by two cover members made of two metal plates, whereby the card is shielded.
In order to increase the volume within a thin card such as a PCMCIA card, the machined metal plates constructing the cover members tend to be thin. As a consequence, the cover members have little strength and are readily deformed. When deformation occurs, the cover members contact the parts inside, causing electrical shorting and mechanical damage to the parts within the card. A common method employed to prevent malfunction due to deformation of the cover members is to place insulating sheets on the undersides of the cover members. Another method is to inject silicone rubber between the board and the cover members.
A card-type image sensor the distal end of which is provided with a camera head for introducing an image has recently been proposed, as illustrated in the specification of Japanese Patent Application Laid-open No. 7-121147.
This card-type image sensor has a main body comprising a signal processor constructed on a board, a card connector provided on one end of the board, and a support portion provided on the other end of the board. The camera head is freely rotatably supported on the support portion.
When this image sensor is loaded in and unloaded from a computer, a connection is made by pushing the card into the computer by hand to insert the card and the card can be detached from the computer by pressing an eject button on the computer body when the card is extracted.
An image sensing device such as a CCD requires a plurality of different voltages, such as two voltages of +15 V and -8 V, as the driving voltages. Though an image sensing device that operates at a single voltage of 5 V, which is employed generally in personal computers and the like, has also been announced, performance is inferior to that of the conventional image sensing device. To obtain better image quality, therefore, it is better to use the conventional CCD requiring a plurality of driving voltages. In order to obtain a plurality of voltages, generally a power supply voltage is acquired from the personal computer and a DC/DC converter is used to provide the plurality of voltages. However, since the DC/DC converter is comparatively large in size and generates a large quantity of heat and noise, it is difficult to incorporate the DC/DC converter in a card-shaped body.
In order to improve the image quality of the camera, it is essential to take measures for dealing with noise with regard to the clock from a quartz oscillator mount on the board, the signal lines of the CCD or the like and the circuitry such as the DC/DC converter for converting and supplying power supply voltage. However, with a camera having a card-type interface of the kind described above, merely providing the metal plates as the cover members of the card affords a shielding effect solely with regard to the exterior of the card.
Further, when a card-type camera is mounted in the card slot of a personal computer or the like and a circuit which becomes a source of heat is placed on the portion of the card inserted into the card slot, heat accumulates inside the personal computer, which is itself a source of heat. The result is a problem in terms of dissipating the heat produced.
Furthermore, since the camera portion of the card projects from the personal computer, this portion of the card is susceptible to excessive external force not only when the card is inserted into and withdrawn from the card slot but also during photography. Since a card such as a PCMCIA card has little mechanical strength owing to its thin metal cover members, as mentioned above, the card is likely to be deformed. When a camera is attached to the structure of such a conventional PCMCIA card as an integral part thereof, the overall length of the card is necessarily extended by the length of the attached camera head. A problem encountered with the structure of this conventional card is its poor mechanical strength.
In recent years great efforts have been made with a view to consolidating interfaces used for the purpose of connecting various electronic devices. To this end, standards such as the above-mentioned PCMCIA have been announced. A variety of information processors such as computers capable of accommodating these standards are now being sold. In addition to the above-mentioned card-type camera, various other electronic devices that accommodate these standards have been announced, such as memory cards, infrared communication cards and fax/modem cards.
Many electronic devices of this kind are internally provided with a mixture of analog and digital circuits. This will be described taking an infrared communication card shown in FIGS. 14, 15 and 16 as an example. The infrared communication card is connected to an information processor having a connecting portion in line with the PCMCIA standards and communicates, by infrared rays, with another device having means for infrared communication.
FIG. 14 is a perspective view showing the external appearance of a card for infrared communication, FIG. 15 is a perspective view showing the interior of the card, and FIG. 16 is an exploded perspective view showing the architecture of the card. The card has an PCMCIA connector 71 for connecting an information processor having a connecting portion in line with PCMCIA standards, and a card frame 72 having a board supporting portion 72a which supports a circuit board 76, described later, and a spring positioning hole 72b.
Metal plates 73 serve as covers and shielding plates. The card further includes such component parts as a digital circuit 74 and an analog circuit 75 mounted on the circuit board 76. A coil spring 78 is inserted into the spring positioning hole 72b and is adapted to electrically connect, by its inherent resilience, a grounding pattern 77 provided on the circuit board 76 and the metal plate 73 constituting the shielding plate. Numeral 79 denotes an infrared diode.
In a case where the infrared communication card constructed as set forth above is connected to an information processor having a connecting portion in line with the PCMCIA standards, the infrared communication card is such that digital data sent from the information processor via a PCMCIA connector are converted to digital data by the above-mentioned digital circuit, and the infrared diode 79 is fired by the analog circuit to transfer data. In order to arrange it so that the card will not be affected by noise produced by the information processor or by external equipment, and in order to prevent the internal circuitry from being damaged by static electricity, upper and lower cases are constructed by the metal plates 73 and these are grounded to the circuit board 76 by the coil spring 78.
In order to raise the processing speed of information processors, however, much higher frequencies are being used in the internal circuitry. Consequently, when an electronic device having a mixture of the analog and digital circuits mentioned above is used upon being connected to an information processor, the analog and digital circuits are disposed without taking any special consideration. As a result, the analog circuit, which is readily susceptible to the effects of noise, may malfunction in the presence of noise.
Further, since assembled parts such as the coil spring 78 are required, the efficiency of the assembly operation suffers.